Lots of engines produce extreme oil pressure pulses at different speeds, either because the oil pump puts out pulses, because various oil passages open and close as the engine turns, or (really) a combination of both. For example, the #4 cam bearing in Mopar v8s I work on "gates" pulses of oil to each bank's rocker shaft one at a time as it spins, and causes a noticeable dip in oil pressure when the passages line up for example, but every main bearing in virtually every engine design is also doing the same thing as the crank oil port aligns with the block oil port. Oil pressure gauges usually smooth those out unless you get an oil tube filled solid with oil on a mechanical gauge, in which case the needle just swings wildly and the gauge "sings" (ask me how I know...). So I can totally envision that a polymer or thin metal cylinder exposed to those pulses would 'buzz'. The real question is "why now and not before?" That's the only red flag for me- what changed, and is it a problem? Are you using a different oil filter cartridge? Did it get installed incorrectly? Is an O-ring missing, or is the ADBV not working right?

Same oil as last year as well.... I replace the oil filter (and o rings) in case it was that but no change.

Copme to think of it, the only work I have done on the oil side is replace an O ring on the oil cooler thermostat as the old one was leaking. I wonder if this is causing a restriction until it opens up (max oil temp).

Same oil as last year as well.... I replace the oil filter (and o rings) in case it was that but no change.

Copme to think of it, the only work I have done on the oil side is replace an O ring on the oil cooler thermostat as the old one was leaking. I wonder if this is causing a restriction until it opens up (max oil temp).

I suppose oil pressure measurement will indicate if this is the case.

It depends on the oil system. Some of them have so much going on that old school "watch the gauge" methods don't work well or at all. Some use the oil pressure sensor to vary the output of the oil pump and maintain a constant pressure... all well and good until something goes wrong and the system compensates and hides the issue until a major failure happens. Or, the sensor goes bad and the oil pressure shoots to max ("safe" mode) and throws a code :-/